Electrode joint



Feb. 21, 1956 H. v. JOHNSON ET AL ELECTRODE JOINT Filed Oct. 12, 1954 INVENTORS Y V. JOHNS HARR NEA Unite States Patent Y., asslgnors to lion,

Niagara Falls, Union Carbide and Carbon Corporaa corporation of New York Application October 12, 1954, Serial No. 461,714 Claims. (Cl. 287-127) This invention relates to a joint between sections of an electric furnace electrode and has for an object to pro vide an improved joint of this class which is easier to make and assemble and has less danger of the pitch melting prematurely.

After the invention of Patent No. 2,510,230 it was disdanger of nipple rupture could be provided by the provision of a pitch reservoir opening onto the end face of an electrode section so that into the pores and crevices and bonded the contacting end faces, thus transmitting much of the flexural stresses between the electrode sections directly without having to have them pass largely through the nipple. The clearance spaces around the nipple threads were substantially free of any pitch thereby enabling the nipple to slide or tilt slightly with respect ment sought the same freedom from fleXure in the nippie with satisfactory electrical conductivity in the end face contact by eliminating the pitch reservoir in the end face and transferring it to each end of the nipple with only about per cent to 25 per cent of the thread clearance space volume being filled with pitch.

According to this invention a satisfactory electrode joint has been developed which possesses the advantages of a nipple that does not have to transmit a major portion of fiexural stresses between electrode sections, has satisfactory electrical conductivity, adequate tightness to prevent an electrode section coming unscrewed with respect to the nipple, foolproofness whereby it is immaterial which end of a section and nipple is at the top or bottom, requires less pitch or other thermal setting bonding material, is one in which it is simpler and easier to form the pitch reservoir and install the pitch therein, and this joint is constructed to reduce the danger of the pitch flowing out of the reservoir prematurely and before the joint has been fully formed.

Specifically the nipple is provided adjacent each end with a diametral or radial recess into which the pitch or other thermal setting binder is inserted. The pitch is preshaped into the form of a stick of a size to be easily inserted in the recesses adjacent each end of the nipple. Upon heating the pitch melts and flows into only about 10 per cent of the thread clearance volume and adjacent each end of the nipple. Preferably the pitch is surrounded by a thermal insulating wrapper which delays the time required for the pitch to melt to an amount such that when the pitch cartridge is inserted in a nipple heated to a temperature above the melting point of the pitch, there will be ample time for the joint to be fully assenv bled after the last stick of pitch has been inserted.

Referring to the drawing:

Fig. 1 is a longitudinal section through an electrode joint embodying this invention;

Fig. 2 is a longitudinal section of a modified construction;

Fig. 3 is an enlarged detail of the area shown within the circle designated 3 in Fig. 1; and

Fig. 4 is a perspective showing the pitch cartridge.

The furnace electrode joint in Fig. 1 comprises a lower electrode section 10, the upper electrode section 11 and the nipple 12 in threaded engagement with each section holding their end faces in mechanical and electrical contact as shown at 13. A diametral recess 14 is bored into the upper portion of the nipple 12 and a similar recess 15 adjacent the lower end of the nipple is also cut. Within each reservoir or recess is a preformed cartridge 16 of pitch having a melting temperature between about C. and 200 C. As is well known in the art the pitch in this cartridge melts on heating. It flows out of its diametral recess into the clearance spaces indicated in where on further heating it carbonizes and bonds the hi pie to the electrode section against the sections coming unscrewed in use. In the present instance the quantity of pitch however, is insufficient to fill all such clearance spaces and only about 10 per cent to 20 per cent of the volume of such clearance spaces is supplied with this pitch and the pitch is located adjacent the ends of the nipple after it has become set. In this way the joint is not so stiff but permits a slight tilting or sliding of the nipple with respect to each section in order that flexural stresses may not in large measure have to be borne by the nipple because the joint is usually of less strength to withstand such stresses than are the electrode sections.

The preformed cartridge of pitch may be a precast, stick which is unwrapped but preferably it is such a stick having a wrapper of thermal insulating material around it as shown in Figs. 3 and 4. Around the outside of the cartridge is a layer of aluminum foil 17 to reflect radiant heat from the nipple from penetrating the cartridge and melting the pitch prematurely. Between the pitch 1? and the foil 17 is a layer of fibrous insulating material to delay conduction of heat from the nipple to the pitch. in this case the fibrous material 18 is constituted by about 14 layers of kraft paper in a cartridge for a 29 inch diameter electrode. The effect of this wrapping is to delay the melting of the pitch 19 as much as one to six minutes before it flows into the helical clearance spaces 20.

In Fig. 2 the pitch recesses 14a and 15a are radial and the pitch cartridge 16a is of shorter length than is the cartridge in Fig. l for the same size electrode and nipple. No large number of radial cartridges will be needed because the clearance space to be filled is small.

Instead of a conductive cementitious binding material like pitch it has been found that a non-conductive cementitious binder may also be used in place of the pitc. but preferably such a binder should be thermal setting. Examples of non-conductive binders include water glass and Saureison cement.

The cartridge recesses in the nipple are drilled adjacent the top and bottom without having to invert or the position of the nipple.

In locations where the electrode sections must be nected close to the top of the furnace due to the absence of headroom or because a long electrode slip cannot be tolerated within the furnace, it has been found that the thermally insulated pitch cartridge of this invention is especially needed. In those installations where large 1" room above the furnace is available the electrode section may be connected far enough away from the furnace roof for the thermally insulated pitch cartridge to be unnecessary. Where the headroom is not large a cartridge is placed into one of the nipple before the nipple is threaded into the heated lower section. The ripple is then screwed into that lower section for half its length. Hours later a pitch cartridge is placed into the upper recess 14 of the nipple just before the upper electrode section is to be secured in place. The threading of each electrode section onto its nipple should take not over a.

, hon contact.

minute and the delay occasioned by the thermal insulation around the pitch is adequate to prevent the pitch from melting prematurely and preventing carbon to car- Another way inwhich the joint is made is to have the nipple with one cartridge inserted into a cold electrode section with the section arranged horizontally, hen when a section is moved to a vertical position a pitch cartridge is placed in the lower end of the nipple just before that nipple is threaded into the hot lower electrode section.

Among the advantages of this invention may mentioned the fact that a suitable electrode joint has been provided which is simple and less costly than have been the prior art joints. A delay of one to six minutes aifords protection against premature melting of the pitch before the parts of the joints are fully assembled. The nipple and the erectrode sections are both capable of being attached with either end upward, thus providing a foolproof joint, that is one in which the workman need not be required to be sure that one end of the nipple or of an electrode section is intended to be at the bottom of the joint. As compared with the joint of prior patent construction 2,510,230 the present joint is free of the disadvantage of having considerable nipple breakage due to the joint being too stiff. As compared with the electrode joint in the prior application of H. V. iohnson, Serial No. 300,243, filed July 22, 1952, the joint of the present invention is more nearly foolproof since either end of either the nipple or the electrode section may be placed uppermost or lowermost but it makes no difference which. As compared to that same prior construction the joint of this invention is slightly more conductive for an electrode of the same size due to the fact that no portion of a meeting of end faces of either electrode section in this invention is prevented from having any good contact with the other or contiguous meeting end face. In that prior mentioned application Serial No. 300,243 a minor portion of the meeting end faces of one or both electrode sections was eliminated from afiording good contact by the ract that a pitch reservoir was formed within that end face. As compared with the joint in the prior application of Johnson et al. 379,566, filed September 11, 1953, for Furnace Electrode Joint, the construction of the present invention requires less pitch because not so much pitch has to remain in the pitch reservoir as is the case in that last mentioned application if it is to be considered capable of comparable foolproofness. In that prior construction the pitch reservoirs were axially disposed and almost half of the pitch in that reservoir was not usable. The drilling of the holes for the pitch in said aforementioned application was more difficult because the nipple had to be turned over after having one pitch reservoir drilled in order for the reservoir at the opposite end of the nipple to be formed.

With a nipple 10.75 by 14 inches the pitch reservoirs 16 and 16a were placed about one and a half inches from each end. The quantity of pitch found desirable is in the range of .02 to .11 of a pound for this foregoing nipple size.

We claim:

1. An electrode joint comprising contiguous electrode sections each provided with a threaded recess in the contiguous endface thereof, a nipple threaded into said recesses and holding said electrode sections with their end faces in mechanical and electrical contact, the threads of said recesses and said nipple providing clearance spaces therebetween when said nipple is tightened in said recesses, the end portions of the nipple being each provided with a bore generally normal to its longitudinal axis and a fusible thermal setting'binder in said bores adapted to run outof said bores when melted and in volume sufficicnt to fili less than a major portion of the thread clearance spaces of the joint.

2. A joint according to. claim 1 is sufiicient to fill no more than the thread clearance spaces.

3. A joint according to claim 1 in which said thermal setting binder is provided with a thermal insulating cover capable of delaying melting of the binder at least as much as between one to six minutes as compared with the time required for melting the binder without such thermal insulating wrapper.

4. An electrode joint comprising contiguous electrode sections each provided with a threaded recess in the contiguous end face thereof, a nipple threaded into said recesses and holding said electrode sections with their end in which said binder about 20 per cent of faces in mechanical and electrical contact, the threads of said recesses and said nipple providing clearance spaces therebetween when said nipple is tightened in said recesses, the end portions of the nipple being each provided with a plurality of bores generally normal to its longitudinal axis and a fusible thermal setting binder in said bores adapted to run out of said bores when melted and in total volume sufficient to fill less than a major portion of the thread clearance spaces of the joint.

5. In a threaded carbonaceous connecting nipple for an electrode joint of the character in which the ends of carbonaceous electrode sections are provided with threaded recesses and a threaded nipple is provided which has its opposite ends entering said recesses and in which the threads of said recesses and said nipple provide clearance spaces therebetween when said nipple is tightened in said recesses; the improvement wherein the end portions of the nipple are each provided with a bore extending inwardly from the threaded surface generally normal to the longitudinal axis of the nipple and a fusible thermal setting binder is carried in said bores, is adapted to run out of said bores when melted, and is in volume suficient to fill less than a major portion of the aforementioned thread clearance spaces when such nipple is embodied in an electrode joint of the character described.

References Cited in the file of this patent UNITED STATES PATENTS 1,921,944 Riebel Aug. 8, 1933 2,033,122 Cornell Mar. 10, 1936 2,352,865 Smith July 4, 1944 2,510,230 Johnson June 6, 1950 2,616,384 McBride Nov. 4, 1952 

1. AN ELECTRODE JOINT COMPRISING CONTIGUOUS ELECTRODE SECTIONS EACH PROVIDED WITH A THREADED RECESS IN THE CONTIGUOUS END FACE THEREOF, A NIPPLE THREADED INTO SAID RECESSES AND HOLDING SAID ELECTRODE SECTIONS WITH THEIR END FACES IN MECHANICAL AND ELECTRICAL CONTACT, THE THREADS OF SAID RECESSES AND SAID NIPPLE PROVIDING CLEARANCE SPACES THEREBETWEEN WHEN SAID NIPPLE IS TIGHTENED IN SAID RECESSES, THE END PORTIONS OF THE NIPPLE BEING EACH PROVIDED WITH A BORE GENERALLY NORMAL TO ITS LONGITUDINAL AXIS AND A FUSIBLE THERMAL SETTING BINDER IN SAID BORES ADAPTED TO RUN OUT OF SAID BORES WHEN MELTED AND IN VOLUME SUFFICIENT TO FILL LESS THAN A MAJOR PORTION OF THE THREAD CLEARANCE SPACES OF THE JOINT.
 5. IN A THREADED CARBONACEOUS CONNECTING NIPPLE FOR AN ELECTRODE JOINT OF THE CHARACTER IN WHICH THE ENDS OF CARBONACEOUS ELECTRODE SECTIONS ARE PROVIDED WITH THREADED RECESSES AND A THREADED NIPPLE IS PROVIDED WHICH HAS ITS OPPOSITE ENDS ENTERING SAID RECESSES AND IN WHICH THE THREADS OF SAID RECESSES AND SAID NIPPLE PROVIDE CLEARANCE SPACES THEREBETWEEN WHEN SAID NIPPLE IS TIGHTENED IN SAID RECESSES; THE IMPROVEMENT WHEREIN THE END PORTIONS OF THE NIPPLE ARE EACH PROVIDED WITH A BORE EXTENDING INWARDLY FROM THE THREADED SURFACE GENERALLY NORMAL TO THE LONGUTUDINAL AXIS OF THE NIPPLE AND A FUSIBLE THERMAL SETTING BINDER IS CARRIED IN SAID BORES, IS ADAPTED TO RUN OUT OF SAID BORES WHEN MELTED, AND IS IN VOLUME SUFFICIENT TO FILL LESS THAN A MAJOR PORTION OF THE AFOREMENTIONED THREAD CLEARANCE SPACES WHEN SUCH NIPPLE IS EMBODIED IN AN ELECTRODE JOINT OF THE CHARACTER DESCRIBED. 